1. Field of the Invention
The present invention refers in improvements made to cutting units for cutting bands of material into strips of a predetermined width.
More particularly, this invention refers to improvements made in cuttings units consisting of the combination of at least one rotating "blade" and a coherent "counter-blade" also usually rotating.
2. Description of the Prior Art
As is known; the cutting units of the type shown above are mainly, but not exclusively used in the paper industry, for the selective cutting of bands of material, generally paper based, of plastic material, as for example polystyrene or other artificial or synthetic polymeric porduct, or other manufactured article which can be cut into strips of a predetermined width.
The starting material is generally supplied in rolls by the manufacturing industry, or in the form of packages of different sizes and variously arranged.
It is also well-known that to reach efficient industrial production, it is necessary or at least economical, to have sevral cutting units available which must be selectively spaced along the length of a structure, generally known as a "beam", whose extremities are supported by "shoulders".
These spacings, obviously related to the dimensions of the starting material to be cut, are established and made with the process stopped, by means of the reciprocal engagement of the supports carrying said blade and counter-blade.
Generally this reciprocal engagement between the supports is ensured by at least one gudgeon fixed to the blade-carrying support which is inserted into a hole of the support, generally a plate, connected to the counter-blade.
In this way, by using a single motor means, the blade - counter-blade unit can be shifted. Several units can be connected to one or more beams and their simultaneous shift guarantees the correct constant spacing between the working surface.
The locking of the unit and the engagement of the blade with the counter-blade are generally done by means of pressurized fluid, generally compressed air, coming from a single source or supply "line", connected to a locking piston of the group on the beam and to an actuator respectively.
The pressurized sent into the actuator also preforms the operation of positioning the rotating blade in relation to the counter-blade. These cutting units are well-known and are widely used in industry, but long experience in the field has revealed that this technology, although technically valid, has some limitations and deficiencies. For example, the locking of the unit and the gudgeon control for the reciprocal engagement of the blade and counter-blade supports, require separate supplies of pressurized liquid and, given the number of the groups, this means considerable complexity of pipes and consequent production and maintenance costs, bulk, etc. Another disadvantage which the known cutting units have is the inevitable phenomenon of wear on the counter-blade, which involves continuous and laborious adjustment each time the unit is shifted.